Imagine for a moment a technology that is simple and universal, and needs no software updates. It is a string of numbers, each portion acting as a precise set of coordinates—so basic and elegant that your great-grandparents could use it. Put the numbers in the correct sequence and the technology immediately triggers a bit of magic: Where seconds ago there was silence and haptic nothingness, all of a sudden there is a glorious burst of sound or vibration miles, even continents, away. Then, if you’re lucky, you hear a voice, and you respond with yours: your questions, your frustrated pleas to speak with a “representative!”

The phone number has been with us in some form since 1879, and unlike carbon paper, VHS tapes, and the Walkman, it is not yet obsolete. Although there are dozens of ways to get in touch now, few are as durable and reliable as picking up the phone. A quick thought experiment: Say you just got in a fender bender or, God forbid, find yourself in a genuine emergency—would you text for help, or would you dial an emergency contact or 911? Although so much of our identities have migrated online, these sequences of numerals are an analog tie to the physical world. When we make an account or need to prove our identity to any given system of machines and networks, we use the string of numbers as a means of authentication.

But the phone number isn’t just the yeoman farmer of the technological landscape—a modest, utilitarian workhorse—it is also a vital cultural touchstone. I am and have always been a man without a county; a person who, because of childhood relocations and general adult restlessness, has had the great fortune to adopt many a hometown, from Manhattan to Missoula, Montana. Despite my wandering, my sense of place and a nontrivial aspect of my identity is forever fixed, thanks to three simple numbers: 610, which is switchboard speak for the “Philadelphia Suburb Zone.” I lived there for only a decade, but it was when I happened to get my first cellphone. My area code thus provides me with something akin to a clever disguise or even a passport. Stumbling upon another 610 number is like opening a door. What town are you from? Oh really, where’d you go to school? Three digits can turn a stranger into a fellow traveler.

Phone numbers, they’re wonderful! A great invention, 10 out of 10, no notes! Call J. G. Wentworth! 877-CASH-NOW! 800-588-2300, EMPIRE (today)! Where would we be without phone numbers? Bored? Lost? Wearing a loincloth and grilling freshly hunted meat over an open flame? I can’t help but feel a little romantic about the fact that, one day in 2003, I stumbled out of a Hot Topic and into a Cingular Wireless store at the King of Prussia mall and emerged with a mostly random 10-digit signifier that I still use to log in to my bank, contact the vet, and text upsetting, AI-generated TikToks to my group chat at 1 a.m. That’s staying power and versatility.

After I tweeted about the role phone numbers play in our lives, a number of people responded to share their own perspectives. A phone number can mark a new occasion, as it did for a user named Austin McKinley, who told me that the first thing he did in 2008 when he moved to San Francisco was buy an iPhone and get a local phone number. “Old life over, new life started,” he wrote. In places such as Maine (and my former Montana), an area code can mean state pride. “Having a non-207 number is an immediate signal of outsiderness,” Twitter user Ben Sprague, a Mainer, told me. “Woe to those from away suffering the slings and arrows of area-code discrimination.” A good number can also be a sentimental tie to the past, as it is for a user located in Philadelphia who goes by Amy, and who told me that she inherited her number from her mother when she died. And my friend John, who tweets as Johnny Courage, holds on to his 919 area code in order to “keep my Carolina bona fides and Southern expat status strong,” he wrote. “It’s a quaint relic of yesterday, sure. But it connects me to home.”

These old-fashioned pleasures shouldn’t suggest that the phone number hasn’t evolved over time. As my colleague Megan Garber wrote in 2014, phone numbers started out as peculiar alphanumeric addresses that served small geographic areas (for instance, MU 5-9975, she wrote, would direct you to a switchboard agent who would then connect you with a line in the Murray Hill neighborhood of New York City). As phones grew more popular, the manual-switchboard system became automated and the number system went from regional to national, with a longer set of numbers and the introduction of area codes. Each time the numbering system has expanded, we’ve grumbled about it, but still, it persists—North America’s current 10-digit numbering system launched in Maryland in 1997, and we haven’t looked back.

[Read: The evolution of the area code]

But even the 10-digit system—one of the technological constants of my life—has an expiration date. At some point, the numbers will run out, a realization that caused me to wonder who, if anyone, is keeping tabs on our numbers. Thankfully, the North American Numbering Plan Administrator, the delightfully bureaucratic organization that manages and assigns phone numbers and area codes in 20 countries, is on the case. Say a whole bunch of people move to Montana or Maine and request new numbers—NANPA’s team works with carriers and state commissions to roll out a new area code, a process that takes at least three years, Florence Weber, NANPA’s senior director, told me.

“We continue to see an uptick in terms of requests for numbers—that’s not going away,” Weber said. But nothing lasts forever. NANPA has been closely monitoring and preparing for the day that we run out of three-digit area codes or have to move beyond the 10-digit number. Weber told me that, according to NANPA’s proprietary prediction system, which takes into account forecasted demands and assignment rates, the “projected exhaustion date” is sometime in 2051.

[Mark Twain: A telephonic conversation (from June 1880)]

I shudder to think what will happen on that day. The dawn of longer phone numbers is one possibility; surrendering to online services is another. The phone number feels a bit like a relic in the age of Zoom meetings, one-tap FaceTiming, WhatsApp, Signal, Viber, DMs, Discord—you name it. Phone numbers were originally conceived as a way to route connections via location, and technically speaking, the internet now does this just as well either via IP addresses or by using the Voice over Internet Protocol. The nerds suggest that we could ditch the numbering system and use a decentralized calling system that works a bit like web addresses do—you get a unique address and purchase a domain, so people can contact you without having to punch in a long string of numbers.

Still, it’s worth considering what we lose if our area codes, prefixes, and line numbers are slowly washed away by the sands of time. If nothing more, it’s worth appreciating these digits—an impersonal series of semi-random numbers that, once they’re yours, take on a new life. When shared, a phone number is the most intimate of invitations, offering boundless possibilities of connection. It moors and orients us. That alone is a small miracle worth celebrating.

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